At the very heart of the Jesus Prayer lies the actual experience of the body as the temple of the Spirit; in other words, the Spirit dwells in our body (see 1 Corinthians 6:19). The concept of the heart that we find in the mysticism of the Jesus Prayer is closely related to the biblical understanding of the heart as the seat and center of various functions of the spirit.
Spiritual masters of nearly all religions often refer to the heart as the seat of wisdom. It is from the heart that wisdom emanates, not from the intellect. Theophan observed, “If the heart is the center of the human person, then it is by the heart that man enters into relation with all that exists.” Later he added, “There is a particular way that leads to harmony among men that is the heart” (The Jesus Prayer in Eastern Spirituality).
Theophan insisted, “You must descend from your head into your heart. At present your thoughts of God are in your head. And God Himself is, as it were, outside you, and so your prayer and other spiritual exercises remain exterior. While you are still in your head, thoughts will … always be whirling about like snow in winter or clouds of mosquitoes in the summer.”
“Lord Jesus Christ, Son of God, have mercy on me, a sinner.”
From Listening to the Heartbeat of God